Gas turbine engines include compressor sections to compress an airflow, combustor sections that combine the airflow with fuel for combustion and generate exhaust, and turbine sections that convert the exhaust into torque to drive the compressor sections. Gas turbine engines may include one or more shaft that transfers torque from the turbine section to the compressor section.
Rotating shafts and other rotating turbomachinery in engines are supported by arrays of antifriction bearing assemblies connected to nonrotating structures. During operation, the rotating shafts and other rotating turbomachinery can vibrate about the engine centerline. If not dampened, these vibrations may cause excessive structural loads and result in damage. Dampers are used adjacent to the bearing assemblies to reduce the amplitudes of vibrations in the rotating shaft that are transmitted to the rest of the gas turbine engine. Coulomb and viscous dampers are two of a variety of dampers that can be utilized. One commonly used viscous damper is the squeeze film damper, which utilizes a small, fluid-filled annular gap between the bearing and a nonrotating housing. Radial motion of the rotating shaft causes relative motion between the bearing and the nonrotating housing, which changes the gap to squeeze a damping fluid within the annulus, dampening the motion of the rotating shaft. The nonrotating housing and the bearing assembly may be connected by a centering spring to support the rotating shaft and to move the bearing and shaft towards the centerline when they become off centered. A centering spring design known as the squirrel cage is often used to connect the housing to the bearing assembly and may include a plurality of circumferentially spaced beam springs, acting as the centering springs. Squirrel cages have several notable disadvantages.